Chain



FIG. 1 is a front view of our design for a chain;

FIG. 2 is a side view of the chain;

FIG. 3 is a view of the outline of a transverse section of the chain;

FIG. 4 is a rear view of the chain in back of the front view; and,

FIG. 5 is a partial perspective of FIG. 1. 

The ornamental design for a chain, as shown and described. 